This invention relates generally to transmissions of the belt drive type with controls and is more particularly related to the class of variable speed transmissions and the class of engine or motor controls exemplified, in part, by the following patents: U.S. Pat. No. 3,664,206 to Clauss Jr.; U.S. Pat. No. 3,704,634 to Schrodt; U.S. Pat. No. 3,731,549 to Kaiser, et al; U.S. Pat. No. 3,811,331 to Moogk; U.S. Pat. No. 4,024,772 to Kumm; U.S. Pat. No. 3,472,099 to Burez, L.D.; U.S. Pat. No. 3,888,139 to Orshansky, E. Jr.; U.S. Pat. No. 3,939,738 to Adey, et al; U.S. Pat. No. 3,898,893 to Hashimoto, M. et al.
All the transmissions of the patents enumerated above, as well as those of the rest of the prior art, obtain changes in their operating speed ratio by an axial movement of one sheave of each pulley. This feature is in marked contrast to the rotary movement utilized in the present invention which gives reduces size, higher efficiency, greater economy of manufacture and use, simplifier belt replacement and permits incorporation of an integrated control to achieve more optimum overall drive performance, such as when applied to automobiles, driven by either internal combustion or electric motors and/or flywheels.
Present variable speed pulley drives discussed in all the above patents except Kumm are of the type using Vee-belts, which are composed of a rubber composition and have a trapezoidal cross section, the belt transmitting rotary motion at one speed from a source of power, such as an engine or motor, to an output power shaft at another speed, the speed ratio being varied in a continuous fashion from a minimum to a maximum as dependent on the geometry of the belt and pulley system. The Vee-belt is compressed between smooth conical sheave sections in each of two pulleys by external axial forces on the sections to apply tension to the belt and friction between the sides of the Vee-belt and sheave sections to prevent slippage. In operation, a force unbalance caused by changes in the axial loading of the sheave sections causes the Vee-elt to change its radial positions in the two pulleys until a force balance is achieved or a limit range stop is reached. For a large transmitted torque the required axial force exerted on the sheaves results in a large compressive load on the Vee-belt, which requires the belt to have a substantial thickness to prevent axial collapse or failure of the belt. The increase in thickness increases its centrifugal force and causes higher belt tension loads. Also, as the belt thickness increases, pulley size must be increased, due to higher stress loads at a given design minimum pulley radius. Further, the typical Vee-belt ust continuously pull out from the compressive sheave load on leaving the pulley, which results in significant friction losses and belt fatigue, affecting overall efficiency and operating life. Consequently, although variable speed pulley drives have successfully used Vee-belts in a wide range of aplications (industrial drives to snowmobiles and even automobiles) they have been severely limited in their power capabilities for more competitive smaller size equipment. This transmission utilizes the same thin flexible flat belt supported on drive elements similar to that of U.S. Pat. No. 4,024,772, but with totally different more compact sheave and actuator, which reduces the transmission size and volume by eliminating the axial movement of the usual actuators. Also, the efficiency of this transmission is improved by reducing the number of bearings and pulley diameter, and the invention gives a design which permits a more simple belt replacement and maintenance as compared to U.S. Pat. No. 4,024,772. Further, this invention permits the use of smaller actuator forces to give the same belt tension, thus reducing the required fluid pressure and pump work. This invention shows how the fluid pressures required for rotary actuators may be controlled to automatically give the minimum required belt tension, preventing slip over the complete torque, range, thus improving the transmission efficiency by reducing bearing losses. Also, this invention permits a simple practical control for changing the output power and/or speed that may be applied directly to operating internal combustion engines or electric motors on or near their optimum overall efficiency schedules for torque and speed.